With the advent of concentrator photovoltaic (CPV) modules including micro miniature photocells and solar concentrator lenses, even minute amounts or specks of condensation between the lenses and photocells can degrade the output of the cells of the CPV modules. Such CPV modules are typically sealed, but may not be hermetically sealed, for example, due to cost considerations. Moisture droplets from condensation can act as tiny lenses and can redirect incident light that would otherwise be precisely focused on the photocells. Moisture and condensation also often leave residues and affect the functionality of the electronics in CPV modules by forming conductive paths in conjunction with other material in the modules. Furthermore, over time, the moisture can create corrosion between dissimilar metals inside the module and deteriorate module performance. When such events occur in solar arrays including a large number of modules, the damage to such arrays can be extensive and/or costly. With some solar arrays including thousands of sealed modules, remedial access to each module is typically impractical and/or prohibitive.
Some traditional approaches for controlling condensation include single-use or regenerative desiccant materials in various industries for protecting consumer goods or products, such as enclosures containing moisture sensitive electronic devices. For example, some regenerative air dryer systems are designed for drying compressed air, and rely on the use of two chambers filled with desiccant. Typically, when one of the chambers is in operation, the second chamber is regenerated using heaters or pressure swing adsorption. The complexity, cost and maintenance of these systems may limit their applicability for drying the air enclosed in concentrator photovoltaic modules. Similar single and multi-desiccant chamber systems, commonly referred to as desiccant beds, are also used for applications in refining petrochemical, chemical, and gas processing industries to extract water or other classes of molecules.
A different class of air dryer systems, which rely on the use of regenerative desiccant wheels, has been developed for regulating air humidity and/or to reduce energy needs for cooling air inside commercial and residential buildings. Some of these systems rely on the use of waste-heat or solar heat collectors as an energy source to regenerate a rotating desiccant wheel. However, the complexity, cost and maintenance of these systems may likewise limit their applicability for drying the air enclosed in concentrator photovoltaic modules.
Another approach for controlling moisture in a solar collector is described in U.S. Patent Application Publication No. 2009/0173376. In particular, this approach provides a first chamber including a solar collector and a second chamber including a desiccant, where the two chambers are thermally coupled and separated by a moisture barrier. The increase of the air temperature within the solar collector chamber during sun exposure induces a pressure increase within the chamber, pushing air through the desiccant chamber and out to the ambient. Conversely, the decrease of the air temperature within the solar collector at sunset (or multiple times during a cloudy day) induces a decrease of the pressure within the solar cell chamber, which pulls ambient air through the desiccant bed and then back into the solar collector chamber. While this approach provides a symmetrical cycle between the desiccant desorption and adsorption phases, it may not be effective in extracting water from within the solar collector chamber should condensation occur.